Recently, building management systems for managing and controlling the equipped apparatuses such as air-conditioners installed in a building using a given monitoring device have been developed. In a prior art building management system, generally, a central monitoring device connected to an upper-level network such as a LAN (local area network) or WAN (wide area network) manages (monitors)/controls multiple equipped apparatuses connected by a lower-level network via a gateway device.
The gateway device is connected between the upper-level network to which the monitoring device is connected and the lower-level network to which the equipped apparatuses are connected. The gateway device converts data (packets) sent from the monitoring device to data processable by the equipped apparatuses and converts data sent from the equipped apparatuses to data processable by the monitoring device. In other words, the gateway device conducts interconversion between the upper-level network protocol used in processing by the monitoring device and the lower-level network protocol used in processing by the equipped apparatuses.
As an example of the above-described gateway device, a gateway device that can connect the lower-level networks of proprietary specifications that are provided by multiple different vendors who are the providers of the equipped apparatuses to the upper-level network is provided (for example, see Patent Literature 1). This gateway device enables each of the multiple vendors to easily configure a lower-level network of a proprietary specification.
In 2003, BACnet (a data communication protocol for building automation and control networks), which is one of the typical upper-level network protocols, was set forth as an international standard ISO16484-5. Since then, an increasing number of vendors provide a device in compliance with the BACnet set forth as an international standard.
The BACnet is often used for a large-scale building. This is because the BACnet standard is suitable for management of a large-scale building. With the BACnet, a gateway device manages a significantly great number of equipped apparatuses and many gateway devices can be connected to the equipment networks.
The above-mentioned central monitoring device, gateway device, and equipped apparatuses constituting a building management system are often provided by different vendors. In such a case, each vendor can conduct a thorough operation verification test on its own device by itself. However, it is not easy to conduct an operation verification test substantially covering the condition after the building management system is actually built.
For that reason, more than a few unexpected problems occur after the building management system is built and actually operated. In order to solve the problems, it is necessary to collect and analyze electronic messages travelling on the networks to acknowledge the situation and identify where the problem occurred and what the problem is. In such analysis, it is necessary to clarify what kind of events occur on the upper-level network and on the lower-level network, respectively, and what kind of cause-effect relationship the events have. In consideration of such circumstances, there is an increasing demand for improved work efficiency regarding collection of electronic messages travelling on multiple networks simultaneously and analyzing the cause-effect relationship between the electronic messages.
As an example of the network analysis device, a network analyzer comprising multiple measuring terminals, a single main frame, and a single terminal adaptor is disclosed (for example, see Patent Literature 2). The multiple measuring terminals measure measurement objects. The main frame controls the measuring terminals and analyzes/evaluates measurement signals received from the measuring terminals. The terminal adaptor switches the connection of the main frame to one of the measuring terminals in a time division manner.